There are today networks/services that provide ways to enhance the bandwidth capacity. Multimedia Broadcast and Multicast Service, MBMS, introduced by 3GPP in Release 6 is intended to efficiently use network/radio resources by transmitting data over a common radio channel, both in the core network and, most importantly, in the air interface of UTRAN, UMTS Terrestrial Radio Access Network. MBMS is targeting high (variable) bit rate services over a common channel. One of the most important properties of MBMS is resource sharing among many User Equipments, UEs, meaning that many users should be able to listen to the same MBMS channel at the same time. The MBMS is also introduced in E-UTRAN, where MBMS transmissions may be performed in the single-cell transmission and Multimedia Broadcast Single Frequency Network, MBSFN, i.e. multi-cell transmission, types. In case of MBSFN, the cells and content are synchronized to enable the terminal to combine the energy from multiple transmissions.
Multiple Input Multiple Output (MIMO) is a known advanced antenna techniques. MIMO implies that both a base station and a UE have multiple antennas. MIMO provides different spatial processing which has the potential to contribute significantly to improve spectral efficiency, diversity, coverage, interference mitigation, etc. In E-UTRA MBMS, the potential candidates for MIMO are either an open-loop transmission diversity scheme, an open-loop spatial multiplexing approach or a hybrid combination of both.
The spatial diversity transmission technologies have been employed in MBMS system. The spatial diversity transmission may be envisaged in various forms such as macro-diversity and combination of the signals from the diverse transmissions.
In MBSFN, macro-diversity inherently exists in cellular systems when the same stream containing data and/or control information is provided from the adjacent cells. However, in order to take advantage of this form of diversity, a mechanism is needed to combine the signals from the diverse transmissions.
Prior-art proposals for maximum-ratio combining (MRC) and selection combining (SC) exist. The MRC technique is known to provide the best performance but severely constrains the relative transmission delays between the cells. Selection combining, on the other hand, relaxes the delay constraint at the expense of a performance loss. The applications of multiple transmit antenna technologies to MBMS network such as space time block coding (STBC) and MIMO are introduced. STBC is a technique used in wireless communications to transmit multiple copies of a data stream across a number of antennas and to exploit the various received versions of the data to improve the reliability of data transfer. MIMO is used in order to enhance the capacity and throughput without any further increase in the transmission bandwidth. It should also be understood that the usage of unicast services using spatial coding also enhances the transmission capacity.
The spatial processes, such as STBC or the like, or temporal diversity schemes, such as time switch diversity coding and MIMO can be contained in one generic structure. These spatial processes, and the potential adaptation spatial processing between (or among) the different spatial processing are termed as spatial coding in this document. However, spatial coding techniques are limited to the antenna setup and application scenarios.